Flexible conduit, such as pipe for medical or surgical use

ABSTRACT

Disclosed is a process for obtaining a flexible conduit comprising a tube and a helical structure. The process comprises extruding a crosslinkable plastic material in a malleable or formable state, so as to form a profiled strip having, as one piece, a web with two mutually complementary marginal edges, and at least one rib projecting on one side from the web; winding the profiled strip about an axis in a helix with touching turns so that the complementary marginal edges of the profiled strip, belonging respectively to two different turns, form between them, directly, a sealed joint; varying and controlling a winding pitch of the profiled strip, in order to modulate and control a quantity of available and formable plastic material of the tube along the length of the conduit; and crosslinking the wound profiled strip.

The present invention relates to a flexible conduit, such as one used ormade for obtaining a sterilizable hose for medical or surgical use, forexample for conveying a gas to a patient, it being understood that sucha conduit may have many other applications.

In accordance with document U.S. Pat. No. 4,343,672, a process isdescribed for obtaining a flexible conduit, said conduit comprising aprofiled strip, having, as one piece, a web with two mutuallycomplementary marginal edges and at least one rib projecting on one sidefrom the web, according to which process the profiled strip is obtainedby extruding a crosslinkable plastic, the profiled strip, after it hasbeen obtained by extrusion, is wound about an axis in a helix withtouching turns, so that the complementary marginal edges of the profiledstrip, belonging respectively to two different turns, form between them,directly, a sealed joint, and the wound profiled strip, with directlytouching turns, is crosslinked in order to obtain a one-piece flexibleconduit.

In practice, and in particular with regard to a hose for medical orsurgical use, a flexible conduit of the type defined above must bejoined, at least at one end, to an end-piece, which in general ishandled, and in particular is repeatedly fitted onto and removed from acomplementary fixed part. This end-piece is generally a piece which issealably attached and fitted onto the said end of the conduit.

Such an end-piece is the cause of many drawbacks.

That region of the flexible conduit which is adjacent to the end-pieceis subjected to repeated bending because of the manipulation of the hoseor of the end-piece and necessarily constitutes a region of weakness.This is particularly true in the case of a hose for medical or surgicaluse, which is continually being connected to and disconnected from afixed part, or fitting, of another hose or of an apparatus, for examplea respirator. Furthermore, and in this application, the repeatedsterilization of the hose also helps to weaken the region adjacent tothe end-piece. In this medical and surgical use, a weak region of thiskind is unacceptable since it contravenes the safety requirements of themedical hose, in terms of sealing with respect to the inside or theoutside of the conduit.

This end-piece also complicates the manufacture of the final hose, byrequiring the manufacture of an independent piece, this piece thenhaving to be sealably fitted onto the flexible conduit. In certaincases, the difference in inside diameter between the flexible conduititself and the end-piece additionally requires the end-piece to beadapted to this variation in inside diameter or requires an additionaladapting piece to be provided and fitted onto the flexible conduit.

The object of the present invention is to remedy these drawbacks.

More particularly, the subject of the invention is a process forobtaining a flexible conduit of the type defined above, making itpossible to obtain, in a monolithic manner, a single piece incorporatingnot only an impermeable internal tube and a helical external structuresupporting the internal tube, but also the end-piece or end-piecesrequired for the use of the flexible conduit.

For this purpose, the invention provides a process for obtaining aflexible conduit comprising a profiled strip having, as one piece, a webwith two mutually complementary marginal edges, and at least one ribprojecting on one side from the web, the process comprising:

(a) winding the profiled strip, after it has been obtained by extrusion,about an axis in a helix with touching turns so that the complementarymarginal edges of the profiled strip, belonging respectively to twodifferent turns, form between them, directly, a sealed joint; and

(b) crosslinking the wound profiled strip, with directly touching turns,to obtain a one-piece flexible conduit, wherein during the winding ofthe profiled strip, the winding pitch of the profiled strip is varied inorder to control or modulate the supply of deformable plastic manneralong the length of the conduit.

The expression “directly touching turns” should be understood to meanthe formation of a sealed joint at each marginal edge of the profiledstrip, this joint connecting, in a sealed manner, without theinterposition of an adhesive, the each marginal edge to the adjacentmarginal edge of an adjacent turn. This joint is obtained directly bybonding between the two adjacent marginal edges, along the entireappropriate grouting outline, for example with straight, obliquelychamfered or “stepped” edges.

Next, by virtue of the above defined process, it is possible, duringstep (a), to vary the winding pitch of the profiled strip along thelength of the conduit, thereby making it possible to control or modulatealong the length of the conduit the supply of malleable or deformableplastic and the amount of material available per unit length.

Preferably, the winding pitch is decreased during step (a), for exampleat one end of the conduit, in order to locally increase the thickness ofplastic available in the malleable or formable state, beforecrosslinking.

If the thickness of deformable plastic is increased in this way duringstep (a) at one or both ends of the conduit, it is thus possible, whilethe plastic is still malleable, to form an end-piece in this thickness.This plastic is then crosslinked in order to obtain a flexible conduitin which the end-piece or the two end-pieces are made as one piece withthe impermeable internal tube and the external surface of the flexibleconduit interrupts or extends the helical external structure.

Preferably, according to step (a), the profiled strip is wound, as itleaves the extrusion die, around a bar which is moved in translation andin rotation, the external cross section of which sets or predetermines,in negative, the internal cross section of the flexible conduit, whilethe plastic is still deformable or malleable.

This operating choice is particularly advantageous in that it allows theinternal cross section to be varied or modified, along the length of thelatter, for example in order to change the internal diameter of theconduit from a nominal value to another value, which is lower or higher,determined by an end-piece or fitting, without any other complementarypiece or component, such as an adapter.

The present invention will now be described with reference to theappended drawing, in which:

FIG. 1 shows a perspective view of a profiled strip as employedaccording to the invention;

FIG. 2 shows an alternative embodiment of a profiled strip, as employedaccording to the invention, again in perspective;

FIGS. 3 to 6 show, in cross section, four different embodiments of aprofiled strip as employed according to the invention, respectively;

FIG. 7 shows, on the left-hand side, a sectional view and, on theright-hand side, a front view of a complete flexible conduit capable ofbeing obtained according to the invention;

FIG. 8 shows schematically an apparatus or rig allowing a flexibleconduit to be obtained in accordance with the present invention.

A flexible conduit 1 (cf. FIG. 7) is obtained according to the inventionfrom a profiled strip 4, which is itself obtained by extrusion,especially of a plastic, for example a silicone in the uncrosslinkedstate.

In general, this profiled strip 4 comprises, according to a one-piececonstruction or structure, a web 4 a, having two mutually complementarymarginal edges 4 b and 4 c, and at least one rib 4 d projection on oneside from the web 4 a.

Moreover, this profiled strip 4 has the following characteristics:

the two marginal edges 4 b and 4 c of the web 4 a of the profiled strip4 are formed as two mutually complementary chamfers, respectively;

the rib 4 d has a rounded cross section at its top; this cross sectionmay be rectangular or triangular, for example;

the rib 4 d has a solid cross section; this cross section may be hollow,as shown for example in FIG. 3; this cross section may in fact be in theform of a bellows, as shown in FIG. 6;

the rib 4 d is located on the same side as one marginal edge of theprofiled strip 4, for example on the same side as the marginal edge 4 b.

In order to obtain and employ this profiled strip 4, a manufacturing rigshown schematically in FIG. 8 is used, this rig comprising:

an extrusion head 11 for extruding plastic (uncrosslinked silicone), thedie 12 of which determines the profile of the strip 4 as defined above;

a bar 13 which can be moved in translation and rotation with respect tothe extrusion head 11;

two tools 14 with rollers, these being able to be moved closer to thebar 13, parallel to the latter, and moved in rotation, in order to form,in the malleable plastic of the conduit, end-pieces of axisymmetricshape.

Immediately on leaving the extrusion head 11, the profiled strip, havingthe characteristics described above, is wound around an axis 5,corresponding to the bar 13 which is moved in translation and rotation,in a helix with directly touching turns so that the complementarymarginal edges 4 b and 4 c of the profiled strip, belonging respectivelyto two different turns, form between them, and directly, a sealed joint6. In this way, the winding, with directly touching turns, in a sealedmanner, of the web 4 a of the profiled strip 4 generates an internaltube 2. Correspondingly, the helical winding of the rib 4 d of theprofiled strip 4 generates a helical external structure 3 which supportsthe impermeable internal tube 2.

In a manner not shown in FIG. 8, the winding pitch of the profiledstrip, at the two ends of the bar 13, is decreased with respect to thepitch in the remaining part of the conduit being produced. This makes itpossible to have at the two ends an additional amount or overthicknessof plastic, in the malleable or formable state.

When the plastic of the strip is still formable or malleable, that is tosay before the elastomer material is crosslinked, the material of theprofiled strip 4, wound as a helix, is formed at the two ends of theconduit 1 by the rotational action of the two tools 14 with a roller,into two end-pieces 7 respectively, these being axisymmetric andintegral with the internal tube 2, the external surface 7 a of whichinterrupts or extends the helical external structure 3 (cf. FIG. 7) andthe internal surface of which forms a continuous surface with that ofthe tube 2.

A flexible conduit, generally having the structure shown in FIG. 7, isthus obtained solely from the extruded profiled strip 4 which, inparticular, supplies the material needed to form the internal tube 2 andthe helical external structure 3, but also the end-pieces 7, by havingreduced the winding pitch at the point where they are located.

Next, this conduit 1 is set in its final form, shown in FIG. 7, bycrosslinking the elastomer.

The present invention also includes the following alternative forms,which may be considered individually or in combination:

according to FIG. 2, the profiled strip 4 has at least two parallel ribs4 d, thereby making it possible in particular to reduce the timerequired for the helical winding operation, using step (a) describedabove;

according to FIG. 5, the part 4 a of the profiled strip 4 has athickness which varies over the width of the profiled strip, away fromthe rib, so as in particular to define a relatively thin helical region,favoring and predetermining the curvature of the flexible product 1;

the web 4 a of the profiled strip 4 has a notch 4 e parallel to the rib4 d, as shown in FIG. 4; this helical notch in the finished conduitfavors and predetermines the curvature of the flexible conduit 1, makesit flexible and allows a concertina-type conformation, in particular forstorage;

the rib 4 d may be located in the middle or center of the web 4 a, asshown in FIG. 3;

the cross section of the rib 4 d may be hollow, as shown in FIG. 3, andtriangular or with sharp corners, instead of being rounded; this crosssection may in particular have the shape of a bellows, or of one elementof a bellows, as shown in FIG. 6.

It follows from the process described above that the thickness isdifferent from, namely greater than, that of the internal tube 2 at theend-pieces 7, thereby strengthening the conduit 2 at its end. Thisincreased strength makes it possible to connect and disconnect theconduit to and from any other piece or fitting, for example onto theconnector of an assisted respiration machine, without in any wayweakening or impairing the flexible conduit.

The internal cross section of each end-piece 7 is not necessarilyaxisymmetric; this internal cross section may in particular have apolygonal shape.

The internal cross section of the internal tube 2 and of the end-pieces7 may vary along the length of the conduit; in particular, it may beslightly frustoconical. Most particularly, at the end-pieces 7, it maybe greater or smaller than the nominal internal cross section of thetube, in order to be able to connect the said end-pieces to any fittingor component of cross section different from the nominal internal crosssection, this being so without any other complementary or addedarrangement.

The inside surface 2 a of the internal tube 2 may be corrugated orstriated, or completely smooth, from one end to the other, includingforming a continuous surface with the internal surface of theend-pieces.

The internal surface of the conduit 1 may be continuous along its entirelength, including the end-pieces 7, in particular without anydiscontinuity, for example in “stepped” form, between the conduit properand the end-piece or end-pieces.

The web 4 a and/or the rib 4 d may include a reinforcement, for examplea woven or non-woven structure, or an insert, which reinforces orimparts other properties or characteristics to the finished flexibleconduit.

What is claimed is:
 1. A process for obtaining a flexible conduitcomprising a tube and a helical structure, the process comprising:extruding a crosslinkable plastic material in a malleable or formablestate, so as to form a profiled strip having, as one piece, a web withtwo mutually complementary marginal edges, and at least one ribprojecting on one side from the web; winding the profiled strip about anaxis in a helix with touching turns so that the complementary marginaledges of the profiled strip, belonging respectively to two differentturns, form between them, directly, a sealed joint; varying andcontrolling a winding pitch of the profiled strip, in order to modulateand control a quantity of available and formable plastic material of thetube along the length of the conduit; and crosslinking the woundprofiled strip.
 2. The process according to claim 1, wherein thethickness of the plastic material of the flexible conduit is increasedby decreasing the winding pitch.
 3. The process according to claim 2,further comprising decreasing the winding pitch at least one end of thetube during the step of winding and forming an end-piece in a thicknessof formable plastic material at the at least one end of the tube.
 4. Theprocess according to claim 1, wherein during the extrusion and winding,the profiled strip, on leaving an extrusion die, is wound around a barwhich is moved in translation and in rotation, and the external crosssection of said bar sets the internal cross section of the flexibleconduit.
 5. The process according to claim 3, wherein the end-piece isformed in the thickness of formable plastic with a roller whichdetermines the external axisymmetric shape of the end-piece.
 6. Theprocess according to claim 3, wherein the end-piece is formed bystamping or die forming.
 7. The process according to claim 4, wherein atleast one end of the bar, an end-piece is added, which sets, at thecorresponding end of the flexible conduit, an internal shape differentfrom that of the rest of said conduit.
 8. A conduit comprising: aprofiled strip having, as one piece, a web with two mutuallycomplementary marginal edges, and at least one rib projecting from oneside from the web, such that the profiled strip is wound about an axisin a helix with touching turns to form a sealed joint between twoadjacent marginal edges, and to have various winding pitches along thelength of the conduit.
 9. The process according to claim 1, wherein theprofiled strip has at least two parallel ribs.
 10. The process accordingto claim 1, wherein the web of the profiled strip has a thickness whichvaries over the width of the profiled strip, away from the rib.
 11. Theprocess according to claim 1, wherein the web of the profiled strip hasa notch parallel to the rib.
 12. The process according to claim 3,wherein the internal cross section of the end-piece is not axisymmetric.13. The process according to claim 1, wherein the internal cross sectionvaries along the length of said conduit.
 14. A sterilizable hose forsurgical or medical use, comprising: a conduit including a profiledstrip having, as one piece, a web with two mutually complementarymarginal edges, and at least one rib projecting from one side from theweb, such that the profiled strip is wound about an axis in a helix withtouching turns to form a sealed joint between two adjacent marginaledges, and to have various winding pitches along the length of theconduit.